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A block is a set of pulleys or sheaves mounted on a single frame. An assembly of blocks with a rope threaded through the pulleys is called tackle. The process of threading ropes or cables through blocks is called "reeving", and a threaded block and tackle is said to have been "rove". [7]
In sailing, a block is a single or multiple pulley. One or a number of sheaves are enclosed in an assembly between cheeks or chocks. In use, a block is fixed to the end of a line, to a spar, or to a surface. A line (rope) is reeved through the sheaves, and maybe through one or more matching blocks at some far end, to make up a tackle.
A sheave or pulley wheel is a pulley using an axle supported by a frame or shell (block) to guide a cable or exert force. A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain.
The name comes from the fact that the arrangement of lines is roughly Z-shaped. Besides the mechanical advantage to pulling, it also uses only part of the total length of the rope for the block and tackle arrangement. The typical configuration (see diagram) uses two single pulleys and two Prusik knot loops or other suitable friction hitches. [2]
A traveling block is the freely moving section of a block and tackle that contains a set of pulleys or sheaves through which the drill line (wire rope) is threaded or reeved and is opposite (and under) the crown block (the stationary section).
A pulley-block has four parts: the shell, the sheave, the pin for locating the latter in the shell and a metal bush, or coak, inserted into the sheave to save wear between it and the pin. Blocks can vary in size and in the number of sheaves. The process of making the shells